In recent years, due to the high convenience of usability even when the user is in transit or out the door, portable devices provided with a function of outputting a sound such as a mobile telephone are becoming widespread. Furthermore, mobile telephones provided with not only the original telephone call function but also the data communication function capable of transmitting and receiving an electronic mail or browsing a home page when connected to the Internet are becoming widespread.
Such a mobile telephone includes, in a housing thereof, an earpiece unit that outputs an earpiece sound, a display unit that is configured by a liquid crystal display, an operation unit that is configured by various operation keys, a mouthpiece unit that inputs a mouthpiece sound, an audio output unit that is configured by a small speaker which outputs a ringtone when receiving an incoming call signal and outputs a music composition when reproducing music compositions, and a storage unit that stores messages etc.
In thus configured mobile telephone, when receiving an incoming call signal, a ringtone is output from the audio output unit, and when the user pushes the speaking start key of the operation unit, speaking over the telephone becomes possible, and the user can hear an earpiece sound output from the earpiece unit by setting the earpiece unit to the user's ear.
Furthermore, a message etc. stored in the storage unit is output from the earpiece unit. For example, in case of enjoying a game etc. by executing a program which is downloaded from a site, the user watches the screen of the display unit and concurrently listens to a music composition or a sound output from the audio output unit.
On the other hand, there has been suggested an electro-acoustic transducer provided with a function of outputting an earpiece sound (receiver function) as well as a function of outputting a ringtone (speaker function), and an attempt is made to mount the electro-acoustic transducer to a mobile telephone so as to reduce the size and weight, and lower the cost of the mobile telephone by making the mounting space thereof smaller.
As the electro-acoustic transducer, employing a configuration in which a speaker unit for outputting a ringtone and a receiver unit for outputting an earpiece sound are unitedly formed (for example, refer to Patent Document 1), and applying a flat panel speaker that comes into practical use in displays of personal computers to a mobile telephone have been considered.
In the flat panel speaker, a screen member to protect the display panel is used as a diaphragm to radiate a sound, and a sound is output from the display screen. On the back side of the diaphragm, an actuator module having a piezoelectric element is mounted, which actuator module is in contact with the diaphragm so as to convey a vibration, and the actuator module vibrates the diaphragm to radiate a sound wave.
As shown in FIG. 1 and FIG. 2, a mobile telephone 101 of this configuration includes a control unit 102 that controls respective units of the main body of the mobile telephone, a storage unit 103 that stores control programs to be executed by the control unit 102 and various data, a radio communication unit 105 that transmits and receives a radio wave through an antenna 104 so as to perform the telephone call processing and data communication in accordance with a predetermined protocol, an audio output unit 106 that outputs an earpiece sound when the user speaks over the telephone and outputs a ringtone when receiving an incoming call signal, a speaker drive unit 107 that drives the audio output unit 106, a display unit 108 that is configured by a liquid crystal display, a vibrator 109 that notifies the receipt of incoming call signal by generating a vibration, a vibrator drive unit 110 that drives the vibrator 109, an operation unit 111 that is configured by various operation keys etc., and a mouthpiece unit 112 that inputs a mouthpiece sound.
The control unit 102 receives an incoming call signal b1 from the radio communication unit 105 (refer to FIG. 2), and judges whether calling performance setup information is set to outputting a ringtone or generating a vibration in case an incoming call signal is detected. That is, the control unit 102 sends a setup information read-in signal b2 to request the calling performance setup information to the storage unit 103, and receives calling performance setup information b3 from the storage unit 103.
In case thus read out calling performance setup information is set to outputting a ringtone, the control unit 102 sends a speaker drive start signal b4 to the speaker drive unit 107 so as to make the audio output unit 106 output a ringtone of large volume, while in case the calling performance setup information is set to generating a vibration, the control unit 102 sends a vibrator drive start signal b5 to the vibrator drive unit 110 so as to start up the vibrator 109.
However, in case of using an electro-acoustic transducer provided with the receiver function as well as the speaker function, it can be assumed that an incoming call signal is received when the user hears a message with the electro-acoustic transducer set to the user's ear, and a ringtone of large volume is suddenly output. Accordingly, in order to prevent a harm to the auditory sense of the user, there has been disclosed a technique in which, for example, in using a folding type mobile telephone, it is determined that the mobile telephone is being used when it is detected that the mobile telephone is in the opened state (extended state), and the volume of a ringtone is gradually made large (for example, refer to Patent Document 2).
It has also been considered that, by employing a technique of measuring the distance between the user and the mobile telephone and prompting a correction in case it is determined that the positional relationship therebetween is inappropriate (for example, refer to Patent Document 3), it is determined that the mobile telephone is being used in case the distance therebetween is equal to or less than a predetermined distance.
Patent Document 1: JP 2004-179701-A
Patent Document 2: JP 2004-146934-A
Patent Document 3: JP 2003-188957-A